Clean room guided conveyor

ABSTRACT

A conveyor system and method that reduces extraneous forces in a manufacturing process is disclosed. The system and method of the invention are particularly directed to handling and processing sensitive materials such as, for example, in clean room manufacturing facilities. These facilities are used in the fields of semiconductor fabrication, hard disk drive manufacturing, biotechnology, biomedical engineering and pharmaceutical engineering. A conveyor system according to the invention includes a carrier and a drive assembly for providing relative movement thereto. A rib or groove extends along the bottom of the carrier parallel to the direction of travel. The rib and groove structures are also intended to reduce mechanical contact between the carrier and the drive assembly, including its components. A reduction of such contact limits the extent of contamination caused by particulate formation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority of U.S. Provisional Application No.60/484,789 filed on Jul. 3, 2003 entitled, CLEAN ROOM GUIDED CONVEYOR,the whole of which is hereby incorporated by reference herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

In general, most manufacturing processes include automated operations toimprove efficiency and overall product quality. One concern withautomation is that materials or products may be mishandled or damaged.These concerns are more significant for manufacturing processesinvolving sensitive materials such as, for example, in the fields ofsemiconductor fabrication, hard disk drive manufacturing, biotechnology,biomedical engineering and pharmaceutical engineering.

These fields commonly use clean room facilities to reduce the likelihoodof the process becoming contaminated. Contamination is a particularissue with semiconductor wafers. Conveyor systems are used in cleanrooms to transport these wafers for processing. The systems are designedto quickly move wafer payloads without creating particles that couldcontaminate the wafers. It is also desired to have a system in which theexternal forces acting on the wafers are minimal.

To achieve these goals, a conveyor system must be stable and move in aconsistent manner. The system should also not produce additionalcontaminants, which occurs when a surface comes into frictionalmechanical contact with another surface. It is also useful to design aconveyor system which requires a minimal driving force to be moved.

The majority of existing conveyor systems impart undesired externalforces to the wafer payload. These systems also have numerous surfacesthat are in frictional mechanical contact with other surfaces. Moreover,there are few systems that are quick enough to meet ever increasingprocess demands. Another design obstacle to consider is the cost ofconveyor construction materials.

SUMMARY OF THE INVENTION

The present invention is directed to a conveyor system that can be usedin a clean room facility. The invention is particularly useful forsystems that handle sensitive materials. These materials are common inthe fields of semiconductor fabrication, hard disk drive manufacturing,biotechnology, biomedical engineering and pharmaceutical engineering.

A conveyor system of the invention includes a carrier or vehiclepropelled by a drive assembly. The carrier generally has a main body anda bottom. The bottom is designed to have a rib or groove that isparallel to the carrier's direction of travel. Preferably, the system isdesigned to curtail undesired external forces from acting on thecarrier. This is accomplished by providing a guidance mechanism whichminimizes frictional contact while controlling lateral deviation from anintended path of carrier travel. The formation of particulate matter isminimized, as is the application of sudden lateral forces to the carrierand its contents by this guidance mechanism.

The invention is also directed to a method of using the describedconveyor system. The method includes actuating the system andcontinuously or selectively moving the carrier.

DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood by reference to thefollowing detailed description of the invention in conjunction with thedrawings, of which:

FIG. 1 is a pictorial view of a first embodiment of the conveyor systemaccording to the invention;

FIG. 2 is a detailed view of a carrier and conveyor of the system ofFIG. 1;

FIG. 3 is a section view of the conveyor system of FIG. 1;

FIG. 4 is a partial section view of the conveyor system of FIG. 1;

FIG. 5 is a pictorial view of a second embodiment of the conveyor systemaccording to the invention;

FIG. 6 is a detailed view of a carrier and conveyor of the system ofFIG. 5;

FIG. 7 is a section view of the conveyor system of FIG. 5;

FIG. 8 is a partial section view of the conveyor system of FIG. 5;

FIG. 9 is a pictorial view of a third embodiment of the conveyor systemaccording to the invention;

FIG. 10 is a detailed view of a carrier and conveyor of the system ofFIG. 9;

FIG. 11 is a section view of the conveyor system of FIG. 9;

FIG. 12 is a partial section view of the conveyor system of FIG. 9;

FIG. 13 is a detailed view of the system of FIG. 9; and

FIG. 14 is a detailed view of the system of FIGS. 1 or 5.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is useful for transporting sensitive materials ina clean room. In a first embodiment, the invention is directed to theconveyor system shown in FIGS. 1-4. The system includes a carrier 10 anda conveyor assembly 12. The bottom surface 14 of the carrier has a rib16 that is parallel to the direction of travel of the carrier. This ribextends the length of the carrier bottom surface. The rib may berecessed so as to not extend beyond the bottom surface of the carrier,may be flush with the bottom surface, or may extend beyond the bottomsurface. While a recessed rib may be less likely to interfere with othercomponents of the carrier system and may experience less wear, aprojecting rib may be useful for supporting the carrier on a solidsurface. The rib preferably has a square or rectangular cross-section.

Alternative embodiments of the rib may include designs in which the ribdoes- not extend the length of the carrier 10 or those that have aplurality of discrete ribs on the bottom of the carrier. Although thepreferred rib is formed integral with the carrier, other designs mayinclude a rib that is, for example, welded or fastened to the bottom ofthe carrier. Furthermore, there may be several continuous ribs thatextend the length of the carrier.

Preferably, the system of FIGS. 1-4 is used to transport semiconductorwafers. The wafers are retained in the carrier 10. The form of thecarrier may vary depending on the type of manufacturing process in whichit is used. For example, a carrier for merely transporting wafers may bedifferent from one that suspends or supports a wafer during fabricationprocesses.

FIGS. 1 and 3-4 also show a drive assembly 20 associated with theconveyor assembly 12 of the system. The drive assembly 20 houses thedriving motors that propel the carrier 10. The assembly also includessensors or other process controls that actuate and control the movementof the carrier 10. Alternatively, the assembly may include hydraulic,pneumatic or electronic control systems.

Fixed to the drive assembly 20 is a drive rail 22. Coupled to the driverail are drive wheels 24 that contact the bottom surface 14 of thecarrier 10. A circumferential surface of the drive wheels is preferablyprovided as a resilient, durable material such as, for example, hardenedrubber. The drive wheels are coupled to the drive rail and driveassembly by drive shafts 26. The drive shafts extend from the interiorof the drive assembly, where they are directly or indirectly coupled tomotors (not shown), through the drive rail, and into the drive wheels.The drive wheels are rotated as the drive shafts rotate. The driveshafts are preferably substantially cylindrical, although othergeometries can be employed. When the drive shafts pass through themidpoint of the drive wheels, balanced rotation is achieved.

The drive shafts 26 may extend to a complimentary wheel on the otherside of the conveyor assembly 12 or may be disposed with an axle 28, asillustrated. In the embodiment illustrated in FIGS. 1 and 2, the axleextends between drive wheels 24 proximate the drive rail 22 to slavewheels 32 proximate a base rail 30. The slave wheels are optionallysimilar to or the same as the drive wheels. The base rail is generallyaligned in parallel with the drive rail. The distance between the baseand drive rail will depend upon the process for which the conveyorsystem is used and the dimensions of the carrier.

The axle 28 may extend through the slave wheels 32 into the base rail30, or slave shafts (not shown), similar to the drive shafts 26, may beemployed. Because the drive shafts and/or axles couple the drive wheels24 to the slave wheels, the rotation of both wheels is synchronized.This synchronized rotation allows the carrier 10 to be uniformlypropelled.

Although the drive and slave wheels 24, 32 are illustrated as occupyingthe same respective horizontal plane, a slave shaft offset may be usedwhen the slave wheels are not all in the same plane. In addition, otheralternative embodiments may not include slave wheels such that thecarrier 10 is supported and propelled by the drive wheels. The drivewheels 24 and drive assemblies 20 may also be provided on both sides ofthe conveyor assembly 12.

In the embodiment of FIGS. 3 and 4, guide wheels 36 take the place ofslave wheels 32 and so are in mechanical communication with the driveassembly via the axle 28.

The drive wheels 24 and slave wheels 32 (FIGS. 1 and 2) or guide wheels36 (FIGS. 3 and 4) uniformly propel the carrier 10 while also supportingthe weight of the carrier. The weight of the carrier may also besupported by passive or non-driven idler wheels 34, as shown in FIG. 1.The need for these idler wheels 34, for guide wheels 36 in addition toslave wheels 32 (FIGS. 1 and 2), and other wheels or embodimentssubsequently described, depends on the length of the carrier bottomsurface 14 relative to the spacing of the drive wheels. When the lengthof the carrier bottom surface is short compared to the spacing of thedrive wheels, idler wheels and passive guide wheels (FIGS. 1 and 2) arenecessary to support the weight of the carrier. In contrast, when thelength of the carrier bottom surface is long compared to the spacing ofthe drive wheels, idler wheels are not necessary, guide wheels take theplace of the slave wheels (FIGS. 3 and 4), and the weight of the carriermay be supported by the drive wheels and the guide wheels coupled to thedrive wheels.

FIG. 2 shows the carrier bottom surface 14, a rib 16, and one of aseries of guide wheels 36 disposed directly beneath the rib 16. Thepurpose of the guide wheels 36 in this embodiment is to maintain thecarrier 10 in the proper lateral position with respect to the conveyorassembly 12. FIG. 14 also provides a detailed view of the rib and aguide wheel. The guide wheel is provided with a central circumferentialsurface 38 having a constant radial distance from an axis of symmetrythrough the guide wheel. On either side of the central surface are edgecircumferential surfaces 40 separated from the central surface byrespective transitional surfaces 42. The guide wheel of FIG. 14 is shownin contact with the lower surface of the rib 16, thus assisting withbearing the weight of the carrier. In alternative embodiments, the guidewheels are disposed such that the central surface is just below thelowest extent of the rib. In either case, if the carrier begins totranslate laterally with respect to the intended path of travel, alateral edge of the rib will come into point contact with one of thetransitional surfaces, thereby urging the carrier back into the properlateral position. Due to the point contact nature of the interfacebetween the rib and the guide wheel, opportunities for particulategeneration are minimized.

In the embodiment of FIGS. 1-2, guide wheels 36 are shown interposedbetween slave wheels 32 on the base rail 30 side of the conveyorassembly 12. As discussed above, if the dimension A between successivedriven wheels is not too great with respect to the length of the rib 16along the carrier bottom surface 14, the guide wheels need not be incontinuous contact with the lowest extent of the rib in order to serve aweight bearing function or may take the place of the slave wheel on theaxle 28 and provide both driving and weight bearing functions. If,however, dimension A in FIG. 1 is greater than the rib length, or is sogreat that the carrier may not be stable as it passes between slavewheels, the passive guide wheels may be in continuous contact with therib lower surface, as shown in FIGS. 1 and 2.

In FIG. 1, the drive wheels 24 and slave wheels 32 are shown to besimilarly designed. These designs allow the outer circumferentialsurface of the drive wheels to be in flush contact with the bottomsurface 14 of the carrier 10. Similarly, the outer circumferentialsurface of the slave wheels is in flush contact with the lower extent ofthe rib 16 of the carrier. Contact of the carrier by the drive and slavewheels is generally intended to straddle the carrier's center ofgravity. Thus, the drive and slave wheels are preferably positionedequidistant from the carrier's center of gravity.

Different processes and applications, however, may require that thedrive and slave wheels 24, 32 contact the bottom surface of the carrier10 at different locations. Moreover, additional wheels, slideablemembers or a third rail may also change the location of the drive andslave wheels. The drive and slave wheels may also contact the main bodyof the carrier in addition to or rather than at the carrier bottomsurface. It will be appreciated that a multitude of wheels and railconfigurations allow the conveyor system to be used in manufacturingprocess having a range of dimensions and layouts such as, for example,those which have turns or an incline and decline.

Another embodiment of the conveyor system is shown in FIGS. 5-8. Thisembodiment is similar to the previously described embodiments exceptthat the rib 116, which extends along the bottom surface 114 of thecarrier 110, is merely used for lateral guidance. Also, the base rail130 (as well as the drive rail 122) is provided with idler wheels 134interposed between the slave wheels 132. As in the previous embodiment,the number of idler wheels between slave wheels (or between drive wheels124 on the drive rail side) depends on various factors including, butnot limited to, the carrier bottom dimensions, etc. The idler wheels 134are used to support the carrier.

In this embodiment, the drive assembly 120, drive rail 122, drive shafts126 and axles 128 are substantially identical to that of the previouslydescribed embodiment.

Guidance of the carrier in this embodiment is accomplished by guidewheels 136, which are similar to those in the embodiment of FIGS. 1-4,though here they are laterally offset from the slave and idler wheels132, 134 on the base rail 130 side of the conveyor assembly 112. Sinceidler wheels are provided on the base rail side of the conveyor assemblyin this embodiment, there is no requirement for the guide wheels to beweight bearing. Thus, as shown in FIGS. 6-8, there is a gap between thelower extent of the rib 116 and the central circumference of the guidewheel 136. While this guide wheel is shown without transitional surfacesintermediate to the edge circumferential surfaces and the centralcircumferential surface such transitional surfaces may also be employedas previously described.

As shown especially in FIG. 6, each of the guide wheels 136 shares anaxis of rotation with a respective idler wheel 134. A shaft 140 may befixed with respect to the base rail 130, allowing the idler and guidewheels to independently rotate thereabout.

It will also be appreciated that the various alternative designs orconstructions of the previously described embodiments are applicable tothat shown in FIGS. 5-8. These alternative designs or constructionsinclude, but are not limited to, different rib positions andcomplimentary wheel locations.

The rib structure previously described is substituted by a groove 216 inan alternative embodiment of the conveyor system illustrated in FIGS.9-12. This grove provides lateral guidance for the carrier 210. Lateralguidance is accomplished by guide wheels 236 that travel within thegroove. The guide wheels 236 in this embodiment are preferably providedwith a simple outer circumference of constant diameter. Because the ribstructure is replaced by a groove, any channels (e.g., channels 44 inFIG. 14) associated with the rib are not required.

Otherwise, this embodiment is similar to those embodiments previouslydescribed. For instance, as illustrated, the guide wheels 236 may bedisposed on a shaft 240 similar to the offset position of the guidewheel 136 in FIG. 6. Thus, the guide wheel shares the shaft with anidler wheel 234. The idler wheel is substantially aligned with a slavewheel 232, which is shown sharing an axle 228 with a drive wheel 224 ona drive shaft 226.

With reference to FIG. 13, the groove 216 is preferably formed with sidewalls that include at least a portion which is angled away from thegroove. This minimizes the contact area between the guide wheel 236 andthe carrier bottom surface 214 forming the groove, which minimizes theopportunity for particulate generation. Preferably, the groove, at itsminimum width, is wider than the guide wheel 236 such that contactbetween the two only occurs in opposition to lateral forces applied tothe carrier 210.

While the guide wheel 236 is shown in contact with a upper extent of thegroove 216 in FIG. 13, thus illustrating a weight bearing function, theouter circumference of the guide wheel may also extend just below theupper extent of the groove 216, such as shown in FIGS. 11 and 12.

It will also be appreciated that the various alternative designs orconstructions of the previously described embodiments are applicable tothe embodiments shown in FIGS. 9-12. These alternative designs orconstructions include, but are not limited to, different rib or wheelpositions. Furthermore, these variations are applicable to any of theembodiments described herein.

It is understood in describing the conveyor system that severaldifferent designs, structures, configurations, geometries and materialsmay be used. For example, the materials of construction may include, butare not limited to, those that are suitable for clean room processes.Suitability of these materials may depend on factors such as theirdegradation during use, which increases the formation of particulatematter. Bearings may also be associated with the various shaft members,axles and wheels. These bearings may also be varied to more effectivelycontrol the conveyor system. As described, each of the embodiments tendto minimize external forces acting on the carrier by limiting surfacessubject to mechanical contact. Limiting such surfaces also reduces thelikelihood of particulate formation.

The invention is also directed to a method for transporting an articlein a manufacturing process. The method includes providing an embodimentof the conveyor system having a carrier for retaining the article and adrive assembly for providing relative movement of carrier. The methodalso involves actuating the drive assembly to provide for continuoustransportation of the carrier and its payload. It will be appreciatedthat the relative movement of the carrier is controlled by the design ofa particular conveyor system.

While the present invention has been described in conjunction with apreferred embodiment, one of ordinary skill, after reading the foregoingspecification, will be able to effect various changes, substitutions orequivalents, and other alterations to the compositions and methods setforth herein.

It is therefore intended that the protection granted by Letters Patenthereon be limited only by the definitions contained in the appendedclaims and equivalents thereof.

1. A transportation system for conveying vehicles, comprising: a firstand second rail, the first and second rails being mutually parallel fromone another; a first and second set of wheels, the first and second setof wheels respectively disposed from the first and second rails andhaving mutually parallel, substantially coplanar axes of rotation inmovable contact with a vehicle disposed on the first and second rail;and a third set of wheels disposed from at least one of the first andsecond rails, the wheels of the third set being mutually parallel andhaving substantially coplanar axes of rotation, and comprising: asubstantially flat outer surface and parallel raised portions, and asubstantially flat recessed portion, the recessed portion in guidingcommunication with the vehicle.